The Syrian Observatory for Human Rights has said air strikes by the Syrian regime on three hospitals in the opposition-held area of Aleppo killed at least 15 people and injured dozens of others.
One of the last six functioning medical facilities in Aleppo, the Al Bayan Hospital, was closed following the strikes on Wednesday.
The UN Children's Emergency Fund (UNICEF) denounced the strikes, which were carried out in the space of three hours.
It said another attack on the UNICEF-supported Al Hakim Hospital, which contains one of the last few remaining paediatric services in Syria, was not the first on the hospital.
Everyone must question their humanity when babies have 2 be taken out of incubators bcuz of attacks on hospitals." pic.twitter.com/ItQDU7o1y7
— UNICEF MENA (@UNICEFmena) 8 Haziran 2016
"Hundreds of medical facilities that provide critical life-saving health care for thousands have been damaged or destroyed. In the past two weeks alone, six health facilities were attacked across the country," UNICEF's regional director Dr. Peter Salama said in a statement.
"Everyone must question their humanity when babies have to be taken out of incubators because of attacks on hospitals."
Wednesday's attacks are the latest in a series of strikes on medical facilities across Syria.
Last week, the National Hospital in Syria's Idlib Province was destroyed in an air strike.
Another hospital, which is supported by Doctors Without Borders (MSF) and the International Committee of the Red Cross in Aleppo, was also attacked just weeks ago.
The attack killed one of the last paediatricians working in Aleppo, Dr. Wasim Muaz.
State department official: Assad is 'delusional & unfit' to lead Syria
The attacks came a day after Syrian regime leader Bashar al Assad said that his forces will continue fighting and the bloodshed will not stop until "every inch of Syria" is taken back.
It was his first major address since an international effort to reach a cessation deal aimed at ending the country’s six-year-long civil war began in February.
The statement is widely seen as the latest signal that hopes of a peace deal are fading fast.
US State Department official Mark Toner said Assad's remarks "show once again how delusional, detached and unfit he is to lead the Syrian people."
He added that the Assad regime had prevented full access to the delivery of humanitarian assistance and had removed medicine and food items from the convoys.
"If the regime continues to prevent full delivery of supplies, the US will consider it to have reneged on its commitment and [to be] continuing a policy of denying food and medicine to needy people as a military tool."
Toner also accused Assad’s ally Russia of inaction on the delivery of humanitarian relief to besieged Syrian people by air, despite the country committing to a June 1 deadline.
Toner said the United States was disappointed that Russia had taken no "demonstrable steps" to support the International Syria Support Group's call for humanitarian aid.